Plastic and glass bottles are commonly employed to contain liquids such as soda, juice, cleaning compositions, and the like. After the bottles are filled with the liquid by an automatic filling machine, the bottle is capped by a capping machine that screws a threaded cap onto the upper end or neck of the bottle.
In a typical capping machine, a series of bottles are supported on a rotating table and as the table rotates, the bottles are moved sequentially through a number of work stations. The bottles are maintained in position on the table by engagement of each bottle neck with recess or notch in a star guide. The star guide engages the neck of the bottle beneath an annular flange or rim on the bottle neck.
To prevent rotation of the bottle during capping, a pair of knife blades are mounted adjacent each notch in the star guide and face upwardly. The blades are adapted to engage the lower surface of the flange on the bottle neck. When downward pressure is applied to the bottle during the capping operation, the blades dig into the plastic flange and serve to prevent rotation of the bottle during capping.
After a period of service, the blades tend to wear and the worn blades may slip and strip plastic from the bottle with the result that strings of plastic hang downwardly from the bottle neck, detracting from the appearance of the filled bottle.
As the capping machines operate at extremely high speed, the service life of the blades is relatively short so that the blades must be frequently replaced, resulting in down time for the machine.
As a further problem, certain types of plastic bottles include loop type handles that are located beneath the flange on the bottle neck. The handles prevent the blades from contacting the lower surface of the neck flange so that the blade mechanism for preventing rotation of the bottle cannot be used with bottles of this type.